Taking Flight towards a Greener Future: The Promise of Sustainable Aviation Fuels

Introduction

Aviation plays a pivotal role in connecting the global community and driving economic prosperity. However, it has recently come under scrutiny for its high greenhouse gas (GHG) emissions.

In the year 2018, the aviation industry was responsible for 1.04 billion tonnes of CO2 emissions, constituting 2.5% of the global CO2 emissions footprint [1]. However, the broader climate impact extends to 3.5% when factoring in non-CO2 greenhouse gases [1]. With the trajectory of air travel demand pointing skyward, a formidable forecast emerges: an unrestrained ascent in CO2 emissions to a staggering 1.8 billion tonnes if no proactive mitigation strategies are implemented [2]. This showed a dual-edged challenge– the imperative to accommodate burgeoning demand while orchestrating an ambitious reduction of emissions, well below prevailing benchmarks.

To confront this challenge, key industry stakeholders, notably airlines, aircraft manufacturers, airport operators, and industry associations, are actively embracing a wide spectrum of measures. These encompass improving operational efficiencies, offsetting carbon emissions, and transitioning towards sustainable fuels. Among the various measures to reduce the aviation sector’s GHG emissions, Sustainable Aviation Fuels (SAF) has the largest reduction potential and the highest market momentum.

SAF is a ‘drop-in’ fuel that can be blended in any proposition with fossil jet kerosene or, in some cases, completely replace it. The use of SAF does not require any modifications in existing aircraft (including the engine), logistics, or airport infrastructure. Another reason for SAF’s popularity is its readiness level. Sustainable Aviation Fuel (SAF) is not a recent endeavour; its efficacy has been demonstrated through its utilization in over 490,000 commercial flights since the pioneering Virgin Atlantic flight experimented with biofuels back in 2008.

In comparison, exploring alternative zero-carbon propulsion technologies like hydrogen or battery-powered aircraft presents a longer timeline for realization, requiring a minimum of a decade due to intricate technical and logistical challenges. The lower energy density of batteries renders them impractical for long-range flights, and the need for the creation of novel engines, storage facilities, and safety protocols for hydrogen, makes them less favourable. The International Air Transport Association (IATA) anticipates the ascent of these innovative technologies beyond 2030, with their contributions projected to lead to a 19% reduction in emissions by the year 2050.[3].

Sustainable Aviation Fuel (SAF)

The term Sustainable Aviation Fuels represents a broad class of unconventional, non-fossil liquid fuels. SAFs are considered ‘sustainable’ despite the CO2 emitted during their combustion since the same amount of CO2 is recycled during the growth of biomass in the case of biomass-based SAF. This can also be captured from the atmosphere in the case of synthetic jet fuels. As a result, SAFs are carbon neutral, resulting in an average 80% CO2 reduction on a lifecycle basis.

Types of SAF

A diverse array of sustainable aviation fuels is also generated from a spectrum of feedstock and harnessed through various conversion pathways. The feedstock can be animal fats, algae, plant-based oils, used cooking oils, sugar-rich crops, organic wastes, and even green hydrogen. Each of these feedstocks undergo specific processing that results in fuels that have similar characteristics as conventional jet fuels.

Considering the versatility of aircraft refuelling across multiple airports, the establishment of international standards for jet fuels has been paramount. The guiding benchmark for the technical certification of Sustainable Aviation Fuel (SAF) is ASTM D7566. A rigorous process entails comprehensive engine and flight testing, the endorsement of original equipment manufacturers (OEMs), and a thorough review by the US Federal Aviation Administration. These steps collectively ensure adherence to safety protocols and technical requirements, thereby culminating in the esteemed ASTM approval. The following exhibit depicts the approved SAF technological pathways. ASTM is currently assessing five other technologies including Shell’s Integrated hydropyrolysis and hydroconversion (IH2), Virent’s Synthesized aromatic kerosene (SAK), OMV’s pyrolysis of plastics, and Indian research institute CSIR’s Single Reactor HEFA (DILSAAF).[4]

Challenges and Possible Solutions

The predominant hurdle in advancing the adoption of Sustainable Aviation Fuel (SAF) lies in its elevated cost when juxtaposed with traditional fossil-based Jet A1. Fuel cost accounts for 30% of an airline’s operational costs making it difficult for airlines to afford high-cost premiums in this low-margin business. Even with fluctuating Jet A1 prices, IATA estimates SAF, with all its variations to cost 2X to 4X times more than any aviation fuel. Airlines can partially reduce these costs by passing down the premiums to environmentally conscious travellers in the form of ‘Green Fares.’ This strategic approach has yielded success thus far, as passengers are demonstrating a preference for SAF-powered airlines even in the face of higher fares [5]. Furthermore, the trajectory foresees a swift decline in costs as production scales up, ultimately positioning SAF to attain competitive parity with fossil kerosene.

Another pivotal challenge revolves around the aspect of scale. The current global aviation landscape demands approximately 340 billion liters of jet fuel on an annual basis. However, in 2021, the utilization of Sustainable Aviation Fuel (SAF) merely surpassed the threshold of 0.1 billion litres. While there was a notable upswing in SAF production to 0.3 billion litres in the following year, it remains uncertain whether this growth will suffice to meet IATA’s interim objective of incorporating 8 billion litres of SAF by 2025. As depicted in the graph below, a rapid and exponential escalation of SAF production is imperative to bridge this gap.

• Conclusion

  Sustainable aviation fuel emerges as the ultimate panacea to the aviation industry’s carbon challenge, offering the potential to slash operational carbon footprint by a substantial 80%. Notably, its compatibility with current aircraft and infrastructure bestows a seamless transition, setting it apart from newer technologies such as hydrogen and electrification. The key to greater SAF adoption is exponential production scale-up and the resulting cost reduction. However, in the meantime, interim support from governments and other stakeholders in the form of policy and financial incentives can greatly reduce the cost premiums incurred from the switch to SAF.

  To facilitate the industrial-scale processing of feedstock in the future, a significant investment in advanced technologies and the establishment of scalable and sustainable feedstock alternatives is imperative. Closer collaboration between fuel producers, engine makers, and research institutes will help realize this necessary advancement.

  The aviation industry stands at a crossroads, where a multifaceted strategy intertwining Sustainable Aviation Fuel deployment, innovative technology research and development, operational streamlining, and the cultivation of sustainable infrastructure holds the key to substantial and enduring emissions reduction. This harmonious convergence lights the path toward a future where the skies are greener, air travel is more conscientious, and our collective journey soars to new heights of environmental stewardship.